Field
The disclosure relates to a method and apparatus for frequency interleaving. More specifically, the disclosure relates to a method and apparatus for structured interleaving of symbols with randomization such that periodic interference patterns affecting performance are substantially eliminated.
Description of Related Art
Conventional wireless communication systems employ one or more interleaving schemes to reduce errors in transmission. Interleaving, for example, may help reduce the number of undetected error bursts especially in channels with memory (i.e., fading channels). Interleaving is generally performed after channel encoding and permutes bits in a regular or predetermined fashion prior to modulation and transmission. Upon reception and after demodulation, a de-interleaving process is performed to restore the original bit sequence. Some orthogonal frequency division multiplexed (OFDM) systems use coding and frequency interleaving to help overcome problems associated with transmitting data over frequency-selective (i.e., fading) channels.
Interleaving exploits frequency diversity by spreading any locally deep fades within the channel across the transmission bandwidth. Block interleaving is one form of interleaving in which a block of bits is inputted to a matrix in one fashion (e.g., row-by-row) and outputted from the matrix in another fashion (e.g., column-by-column). Writing the data in sequential order along rows or columns does not maximize the separation of the interleaved bits. Further, block interleaving and other conventional interleaving schemes spread the noise in a predictable manner and are susceptible to reemergence of periodic interference and/or noise.